Metallic resistor element



June 9, 1931. BAILY 1,809,227

METALLIC RESISTOR ELEMENT Filed March 11, 1926 3 Sheets-Sheet l gwuanto'a T1? Ba fly n 9, 1 3 T.F.BA1L'Y 1,80 ,221

METALLIC RES ISTOR ELEMENT Filed March 11, 1926 3 Sheets-Sheet 2 my a - June 9, 1931. F 1,809,227

METALLIC RESISTOR ELEMENT Filed March 11, 1926 5 Sheets-Sheet 3 attmqo Patented June 9, 1931 UNITED STATES THADDEUS F. BAILY, OF ALLIANCE, OHIO METALLIC RESISTOR ELEMENT Application filedMarch 11, 1926. Serial No. 93,893.

The invention relates to resistor elements for heating electric furnaces and the like and more particularly to a tubular metallic resistor consisting of substantially straight tubes connected at alternate ends by return connections, which in some cases may be hollow to form a continuous enclosed passage throughout the entire resistor.

It is well known that solid metallic resistors are in common use in the form of solid wire, ribbon and cast grids. In all solid sections however, the cross sectional area of the resistor is greater for the exposed surface than a hollow section, and since one'of the limiting factors of the heat radiating capacity is the surface area of the ireslstor, the larger the surface area with reference to the cross sectional area, the greater is the heat delivery power for a given weight of metal used in the resistor.

This is especially true in the case where a tubular resistor is located in a furnace and the outside surface radiating heat to the furnace chamber and a fluid is forced throu h the inside of the tube, absorbing heat from the inside surface of the tube and finally delivering the heat into the furnace chamber preferably impinging this heated fluid upon the material to be heated.

In such instances itis preferable to maintain the fluid in closed circuit particularly if it is desired to maintain the furnace under reducing or neutralizing atmosphere, the circulation being maintained by means of a fan having discharge and inlet pipes outside of the furnace, the discharge end connectin with one end-of the resistor tube and the in et with the. furnace chamber.

The tubular shape of the resistor has more mechanical strength, and radiating surface, compared with its mass than any solid cross sectional shape of resistor such as are now in common use, and while I show-round tubes in the drawings, my invention applies to any tubular shape. I I

Another advantage is that the tubular resistor illustrated in the drawin s does not require the use of hangers as 0 all other types of metallic resistors, A further object of the invention is to proreturn bends being constructed so that the contact between the tubes and return castvide a resistor unit that is free to eirpand longitudinally, as in the case of a resistor arranged with vertical tubes, the return castings connecting the bottom ends of the tubes rest on a firm base at the bottom, usually the furnace hearth itself, these castings being of sufficient area to prevent the vertical tubes leamng; or the tubes may be inclined at the top to touch the furnace wall but are not of necessity fastened thereto.

In the case where the tubes run lengthwise of the furnace, then suitable blocks of refractory, non-conducting material may be placed between each pair of return blocks to prevent any sagging or electrical contact between straight sections of the resistor.

A further object of the improvement is to provide a resistor which may be easily and quickly assembled or dismounted when it is necessary to make any repairs thereto, and with a minimum number of parts for such assembly, as the return bends are substantially identical and the tubes of identical cross section in any given installation; the

connection with the tubes may be formed by expanding the 'tubes with an ordinary tube expander against the smooth surface of the hole provided in the return casting to receive the tube, or the tube end may be welded to the inner ring of the return casting if desired.

Another advantage of the tubular resistor is that the exterior surface of the tube is of .such shape that substantially all of the heat rays radiated therefrom will be either directly radiated toward the interior of the fur nace chamber or against the wall and reflected therefrom toward the interior of the furnace chamber, between the tubes which are spaced from each other sufficiently to allow for such radiation without undue. heat pocketing, this space being preferably substantially the diameter of the tube.

In the construction of these resistor units each given section for any one part of the furnace is constructed of tubes of uniform diameter and cross sectional area of metal, the return bends, however, and the area of ings being of greater cross sectional area than the tubes.

In this way the heating effect of the current is less at the connections and in the return bends than in the tubes, and these portions of the resistor therefore run cooler, preventing any hot spots at these points.

- If it is desirable to circulate a fluid through the tubes and return bends, these bends may bexcast hollow, one face of the casting being providedwith holes for receiving the ends of the tubes, the opposite face being provided with a removable cover plate and convenient means for fastening the same, such as is common for fastening the headers inwater tube boilers.

Such an arrangement gives access to the ends of the tubes for welding or otherwise fastening. them to the return castings, enabling, where the tubes are located longitudinally with reference to the furnace walls, for

welding or otherwise connecting the tube and return fitting from the outside of the furnace. Doors in the furnace walls may be prov ded for obtaining easy access thereto.

An embodiment of ,he invention above set forth in general terms is illustrated it the accompanying drawings, in which Fi ure 1 is a vertical longitudinal section of a urnace provided with the improved resistor showing the tubular portion thereof located horizontally;

Fig. 2, a plan sectional ,view thereof;

Fig. 3,-a transverse sectional view of the same Fig. 4, a view similar to Figure 1 showing the tubular portions of the resistor located vertically;

Fig. 5, a transverse sectional view through a furnace showing the tubular portions of the resistor of arch shape;

Figs. 6, 7 and 8, detail sectional views of different forms of connecting the tubular pogtions of-the resistor to the return bends, an

Fig. 9, a diagrammatic sectional view of a portion of the resistor showing the direct and reflecting heat radiation.

Similar numerals of reference indicate corresponding parts throughout the drawings.

The invention consists primarily in ametaHic resistor formed of a plurality of spaced parallel tubes of suitable heat resisting alloy connected at alternate ends to form a continuous, sinuous resistor. These tubular portions may be straight and either horizontal as shown in Figs. 1, 2 and 3 or vertical as shown in Fig. 4; or these tubular portions of the resistor may conform more or less to the contour of'the furnace as shown in Figure 5..

- I The end connectlons upon-these resistors are preferably in the form of return bends illustrated in the drawings whereby the resistor is hollow and gas tight through its length to permit a fluid to be passed therethrough and impinged upon the material within the furnace.

Referring first to Figs. 1 to 3 inclusive, the

furnace '1, which is indicated conventionally The register may comprise a plurality of.

spaced horizontally disposed tubes 4, formed of suitable heat resisting alloy and connected at alternate ends by the return bend connections 5 which are illustrated in detail in Figs. 6 and 7.

These. return connections may be provided with the flared or conical sockets 6 into which the ends of the tubes may be expanded as shown at 7 in Fig. 6, or to which the ends g f the tubes may be welded as shown at 8 in In order to permit access to the interior of.

the coupling members to connect the tubes or disconnect them a removable plate 9 may be provided at the outer side of each coupling member and normally held in closed position as by the bolt 10 and bar 11 in much the same manner as the header of a tube boiler.

Bricks of refractory material as indicated at 12 may be placed between the return fittings or between the tubes to support the same in spaced relation. ,One side of an electric circuit may be connected to each end of the resistor by means of a tubular connection 13 surrounding the end portion of the resistor and extended through the furnace wall.

For the purpose of passing a fluid, such as a reducing or deoxidizing gas, through the resistor and impinging the sameupon the ma terial within the furnace, a fan 14 may be circulating from the fan through the resistors where it is quickly brought to ahigh temperature and then impinged upon the incoming material for the purpose of preheating, deoxidizing or otherwise treating the same.

For the purpose of obtaining easy access to the return fittings a removable wall section 19 is preferably provided in the end walls of the furnace adjacent to each resistor. By removing this removable wall section and the plates 9 upon the return fittings access may be had to the connection of any desired tube to permit removal of a defective tube and replacement of a new tube.

If desired, the tubular portions 4 of the resistor ma be located vertically as shown in Fig. '4. n this case the furnace, as well as the means for forcing fluid through the resistor may be of substantiall the same construction as illustrated in elusive.

The tubular portions of the resistor may if desired be shaped to conform to the general shape of the furnace as for instance theinverted U-shaped tubes 4 shown in Fig. 5 connected at alternate ends as by the return fittin s 6.

s illustrated in Fig. 8 the exterior surface of the tubes is'such that substantially all of the heat rays radiated therefrom w1ll be either directly radiated toward the interior of the furnace chamber or against the wall and reflected therefrom toward the interior of thefurnace chamber between the tubes which are spaced from each other sufliciently to allow for such radiation without undue heat pocketing, this space bein preferably substantially the diameter of t e tube.

It will be seen that the resistor is practically self-supporting, needing no hangers or guides u on the furnace wall to support the same an that it is free to expand longitudinally in the direction of the tubes and any permanent growth, which is common in metals such as iron chrom1um,n1ckel chrome IIOII or. other alloys used under high temperatures will be thus taken care of by the ability of the resistors to freely expand.

Although the improved resistor is illustrated and described as bein primarily designed for electric furnaces it s ould be understood that the resistor may be used in the generation of steam, being located in a suitable setting, the resistor tubes themselves having the water inside in the manner of a water tube boiler.

I claim:

1. A resistor element comprising a plurality of straight, horizontally disposed portions, connections at alternate ends of the straight portions means connecting the straight portions with the connections, and means for supporting said connections upon each other and insulating the connections from each othera 2. A resistor element comprising a plurality of straight, horizontally disposed portions, connections at alternate ends of the straight portions means connecting the.

V straight portions with the connections, and

insulation blocks interposed between and contacting with adjacent connections.

3. A resistor element comprising a plurality of straight, horizontally disposed portions, connections at alternate ends of the straight portions means connecting the straight portions with the connections, and

igs. 1 to 3 ininsulation supporting blocks interposed be- I :iween and contacting with adjacent connecone.

'4. A resistor element comprising a plurality of straight portions, connections at alternate ends of the straight portions means connecting the straight portions with the connections and insulation blocks between and contacting with adjacent connections.

5. A resistor element adapted to be mounted upon the floor of a furnace and comprising a plurality of straight, horizontally disposed portions connected at alternate ends to form a sinuous resistor grid, and insulation blocks located between the end portions of said straight portions for entirely supporting each straight portion upon the next lower straight portions.

6. A resistor element adapted to be mounted upon the floor of a furnace and entirely free from an adjacent wall thereof and comgrising a plurality of straight, horizontally isposed portions connected at alternate ends to form a sinuous resistor grid, and insulation blocks located between the end portions of said straight portions for entirely supporting each straight portion upon the next lower straight portions.

7. A resistor element adapted to be mounted upon the floor of a furnace and comprising a plurality of straight, horizontally disposed portions,-connections attached to alternatev ends of the straight portions, and insulation blocks located between the connections for entirely supporting each connection upon the next lower connections.

In testimony that I claim the above, I have hereunto subscribed my name.

Y THADDEUS F. BAlLY. 

